LO / FLO
Hayward
Intermittent Flow Sensing Fault
Heater intermittently shows LO or FLO and cycles on and off; sometimes heats briefly then shuts down.
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Marginal pump flow rate, Variable-speed pump set too low, Partially clogged heater inlet screen, Failing flow switch or pressure switch
How to Fix / Troubleshooting
Safety First: Turn off power before opening the heater. Do not bypass safety switches for normal operation.
- Increase pump speed: If using a variable-speed pump, temporarily raise RPM to the manufacturer-recommended speed for heater operation and see if the error disappears.
- Clean skimmer and pump basket: Remove leaves and debris that can reduce flow.
- Inspect heater inlet: Check for any external strainers or unions at the Hayward heater inlet that may be clogged. Clean as needed.
- Check flow/pressure switch: Locate the flow or pressure switch on the manifold. Inspect wiring and ensure the switch paddle or diaphragm is not stuck. Replace if intermittent.
- Hydraulic check: Ensure there are no closed valves or partially closed diverter valves in the heater loop. Correct any plumbing restrictions.
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Repair Difficulty
Medium
3/5
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